Non-linear beam dispersion devices



May 22, 1956 B. C. GARDNER ET AL NON-'-LINEAR BEAM DISPERSION DEVICES Filed March 10, 1952 3 Sheets-Sheet 1 004 7. C O/l/ 7 E01.

A770 A/ y May 22, 1956 B. c. GARDNER ETAL' 2,747,035

NON-LINEAR BEAM DISPERSION DEVICES 3 Sheets-Sheet 2 Filed March 10, 1952 l/VPUT VOLT/76C 0 BE A WHO/U5 AWBEAT 4 0/1/65? 5 y MM A770,? :7

May 22, 1956 B. c. GARDNER ETAL 2,747,035

NON-LINEAR BEAM DISPERSION DEVICES Filed March 10, 1952 3 Sheets-Sheet 3 (a) /l l f VI INVENTORS' BERNARD C. GARDNER ROBERT M. UNGE/Z A TTORNE V United tates NON-LINEAR BEAM msransrors nnyrcns Application March it), 1952, Serial No. 275,8d9

7 Claims. (Ci. tl-27) This invention relates to a beam dispersion electron discharge device having non-linear output characteristics, such as the square law characteristic.

The non-linear output tubes have many applications; for example, a tube having the square law output is in considerable demand in performing squaring operations on signals and is also used in linear modulators of the suppressed carrier type, four quadrant multipliers of quadratic type, untuned frequency doublers, instantaneous phase meters and square law detectors.

In accordance with this invention, an electron discharge device is so arranged that the cross-sectional diameter of an electron beam therein is varied with an input signal applied to one of the electrodes. The total beam current is maintained constant while the portion of the beam current collected by a target anode arranged coaxially with the central axis of the beam varies in accordance with the ratio of the target anode area to the cross-sectional area of the beam. For example, if the area of said anode is equal to the cross-sectional area of the electron beam, the entire beam will impinge upon the anode and the anode current will be a maximum. if the beam diameter is increased further, that portion of the total current impinging upon the anode will be reduced by a factor depending in part upon the size and configuration of said anode and upon the voltages applied to the electrodes of said discharge device.

The structure for production of square law output may comprise an electron gun including a cathode, beamforming electrode and accelerating electrode. The latter insures constant beam current in the electron discharge device. A beam dispersion electrode is provided for varying the cross-sectional area and thus the density of the electron beam. Two anodes are provided; the first or target anode is axially aligned with the beam and its area maybe equal to the minimum cross-sectional area of the beam, while the collector anode may be in the form of either a disk or plate larger than the target anode or a coating of conducting material on the inside of the tube envelope. The collector anode serves to collect that portion of the electron beam not striking the target anode. If desired, both anodes may be connected through a resistor across which output voltages may be developed having the desired wave form. The production of a square law output depends upon the target anode shape. By appropriate alterations of the target anode, the output characteristic can be made to conform to any desired curve.

In the drawings:

Fig. l is a schematic diagram of the electron discharge device according to the invention;

Fig. 2 is a fragmentary view showing one embodiment of the anode assembly of the electron discharge device of Fig. 1;

Fig. 3 is a fragmentary view disclosing a second embodiment of the anode assembly of the electron discharge device of Fig. 1;

2,747,085 Patented May 22, 1956 Fig. 4 illustrates a typical target anode for use with the electron discharge device of Fig. 1;

Figs. 5-7 are curves illustrating the operation of the device shown in Fig. 1; and

Figs. 8 and 9 illustrate typical input and output wave forms of the device of Fig. 1.

Referring to Fig. 1, the beam tube electron discharge device has an evacuated envelope 1, containing a cathode 2, beam forming electrode 3, accelerating electrode 4, beam dispersion electrode 5, target anode 6 and collector anode 7 in that order. Cathode 2, which may be any conventional type of directly or indirectly heated electron source, is maintained at ground potential. Beam-forming electrode 3 is. a focusing electrode, which may be in the form of a ring or a metal cylinder whose axis is coincident with the axis of tube 1; this electrode is placed adjacent the cathode and is maintained at an appropriate negative potential, say, minus twenty volts with respect to the cathode, by means of a battery or other unidirectional source 8, as shown in Fig. l.

The electrons in the beam are projected toward and accelerated by accelerating electrode 4, which is an apertured electrode operated at a positive potential (approximately one hundred volts) relative to the cathode. The electrons which leave the cathode surface in random directions are conveyed toward the axis of the tube by the action of beam-forming electrode 3. Together, cathode 2, beam-forming electrode 3 and accelerating electrode 4 comprise a conventional electron gun.

The number of electrons passing through the accelerating electrode, that is, the total current flow in the tube, depends upon the relative potential of the accelerating electrode relative to the cathode. The accelerating electrode insures constant beam current for given values of electrode voltages. The beam dispersion electrode 5, which may be in the form of a ring or a metal cylinder, serves to vary the beam diameter and thus the density and may be selectively connected to various points on a unidirectional voltage source 9. An input signal is connected across resistor 15.

The target anode 6 is axially aligned with the electron beam and is connected through a resistor 10 to the positive end of battery 9. The collector anode 7, which may be either a flat plate or a toroidal disk, is arranged adjacent target anode 6 and has an area considerably greater than that of the target anode. Collector anode 7 is connected through a resistor 11 to the same point on battery 9 as target anode 6, so that the two anodes are maintained at the same potential. Collector anode 7 collects that portion of the electron beam not striking the target anode.

One possible arrangement of the anode structures is shown in Fig. 2 and comprises a target anode 6, which may be either a soliddisk or a toroidal disk of the type shown in Fig. 4. The target anode may assume various configurations depending upon the type of output characteristic desired. The target is supported within the tube by conducting supports 2% which may be welded or otherwise connected to the target anode and connected to base pins sealed in the base of the tube. A collector anode 7 is positioned between target 6 and the end of the tube remote from the cathode. The collector may be supported by supporting wires or rods 21 in the same manner as the target anode.

An alternative arrangement of the anode structures is shown in Fig. 3 in which a target anode 6 is positioned as in Fig. 2 and the collector anode assumes the form of a coating 7 of conducting material on the inside of the tube envelope and insulated from the target. A connection or lead 22 may be sealed into the envelope and connected to the coating in a conventional manner, as shown in Fig. 3.

In operation, a bias voltage adjustable by beam diameter control 12 varies the amount of dispersion of the constant-current beam in the absence of an input signal. The diameter of the beam and hence the number of beam electrons able to strike the target anode 6 are initially adjusted by control 12. If an imperforate target anode 6 is used, the bias voltage Vb may be set to the point at which the beam diameter is just equal in cross section to that of the target anode; this corresponds to maximum target anode current with no input signal. When an input signal is applied across resistor 15, the potential on beam dispersion electrode 5 is varied and the diameter of the beam is thereby varied. Consequently, the number of electrons striking target anode 6 is varied; since the total anode current, that is, the total beam current, is constant, the number of electrons striking collector anode 7 is varied in the opposite direction.

Now, if a positive-going input signal is applied to dispersion electrode 5, causing an increase in beam diameter, the proportion of the total number of electrons in the beam striking target anode 6 will obviously decrease while the number of electrons missing target anode 6 and striking positive collector anode 7 will increase. In other words, the target anode current decreases as the input voltage becomes more positive than Vb while the collector anode current simultaneously increases. The output of the tube may be taken across either terminals 13 or 14, depending upon the tube characteristic desired. Since the output voltages across resistors 10 and 11 are proportional to the target anode current and collector electrode currents, respectively, the characteristic curves of voltage output versus signal output for the aforesaid two outputs will be substantially the inverse of one another.

The output characteristic of the tube will depend, in part, upon the target electrode shape, and the output characteristic can be made to conform to any desired curve by appropriate alterations of the target electrode. For example, if the target anode be in the form of a ring whose inner radius r corresponds to the minimum electron beam radius and whose outer radius r is three times r,, as shown in Fig. 4, the target anode current will vary substantially in the manner shown by curve IT of Fig. 5. When the beam radius is equal to the inner radius of the target anode, all the beam electrons pass through the target anode to the collector anode without impinging upon the target anode. The target anode current, therefore, is zero. As the beam radius is increased, more and more of the beam electrons impinge upon the target and a smaller proportion of the total number of electrons passes through the aperture in the target anode. The target anode will rise to a maximum when the beam radius equals that of the outer radius 1-,, of the target ring 6. As the beam radius is further increased, the outermost portion of the electron beam, as well as the innermost portion, fails to strike the target anode and the target anode current will commence to decline until eventually the greater proportion of the electron beam lies without the area of the target anode.

By proper design and positioning of the beam dispersion electrode 5, the cross-section diameter of the electron beam may be made to vary in a linear relation with the input signal. Moreover, the target output voltage across terminals 13 is directly proportional to the target anode current. The relationship between the target anode output voltage and the input voltage applied to the beam dispersion electrode 5 is shown in Fig. 6. Because of the above-mentioned linear relationships between beam diameter and input signal, as well as between anode current and anode voltage, the curve ET of Fig. 6 is similar to the curve IT of Fig. 5.

As previously stated, the electrons in that portion of the beam which does not impinge upon the target anode necessarily fall upon the collector anode. Since the total beam current is maintained constant, the collector anode current for any instantaneous value of potential on the beam dispersion electrode must equal the total current minus the target anode current. The curve of collector anode output voltage versus input voltage is shown in curve E0 of Fig. 6. The characteristics of Fig. 6 may be varied by varying the diameter or configuration, or both, of the target electrode.

If a square law characteristic is desired, the target anode may be in the form of a flat circular imperforate disk or plate and the collector anode may comprise a flat plate which may preferably be a circular plate conforming approximately to the upper portion of the tube envelope. With such an arrangement the characteristic shown in Fig. 7 may be obtained. If the beam radius is increased from a minimum value equal to the radius of the target anode, the proportion of the beam striking the target anode varies inversely as the square of the radius of the beam. For example, if the beam radius is double the minimum value, the area of the beam is quadrupled and the percentage of the total electrons striking the target anode is obviously reduced to one quarter of the former value, and hence the output voltage across terminals 13 is as shown in curve ET in Fig. 7. Simultaneously, the collector anode collects more and more electrons as the beam radius is increased. Since the total number of beam electrons is substantially constant, the characteristic curve Fe for collector anode output is substantially inverse to the characteristic curve E0 of target anode output, as shown in Fig. 7.

Fig. 8 illustrates approximately the effect of the characteristic of Fig. 7 on an input signal. Assume that the input signal is a saw tooth wave, as shown in Fig. 8a. If the tube has a square law characteristic, such as shown in curve E1 of Fig. 7, and a bias voltage Vb necessary for maximum target current obtains, the output voltage across terminals 13 will be as shown in Fig. 8b. As the instantaneous input voltage of Fig. 8a rises linearly, the beam diameter increases linearly, and the target anode current decreases as the square of the input voltage, as shown in Figs. 8b. The output voltage across terminals 14 will be as shown in Fig. 8c and increases as the output voltage across terminals 13 is decreasing.

If the bias voltage is increased to a new value V'b, as shown in Fig. 9a, the waveform remaining the same, the output voltages across terminals 13 and 14 are as shown in Figs. 9b and 90, respectively. It will be noted in Fig. 9b that the minimum beam diameter is greater than that of the target anode by the amount that bias V'b exceeds Vb. With no signal, therefore, there will be considerable collector anode current so that the target anode current and consequently the target output voltage will not reach the maximum value represented in Fig. 8b. Similarly, since, with the bias voltage V;;, there is al ways collector anode current, even in the absence of an input signal, the collector voltage output of Fig. never reaches zero as in the case represented by Fig. 80. It is evident, therefore, that the output waveform derived from the tube for a given input signal is also dependent upon the magnitude of the bias voltage applied to the beam dispersion electrode in the absence of an input signal.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting electrons and electrode means for forming an electron beam, at first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, a second anode positioned adjacent to said first anode and adapted to intercept that portion of said electron beam not intercepted by said first anode, a beam dispersion electrode positioned within said tube between said electrode means and said anodes and responsive to an input signal applied thereto for varying the cross-sectional area of said beam to thereby vary the number of electrons striking each or said anodes, and separate circuit means connected to each of said anodes for independently deriving conjugate output voltages therefrom which vary inversely with respect to one another.

2. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting electrons and electrode means for forming an electron beam, a first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, said first anode having a substantially circular cross section transverse to the direction of propagation of said electron beam, a second anode positioned adjacent to said first anode and adapted to intercept that portion of said electron beam not intercepted by said first anode, said anodes being maintained at the same positive potential relative to said cathode, a beam dispersion electrode positioned within said tube between said electrode means and said anodes and responsive to an input signal applied thereto for varying the cross-sectional area of said beam to thereby vary the number of electrons striking each of said anodes, and separate circuit means connected to each of said anodes for independently deriving conjugate output voltages therefrom which vary inversely with respect to one another.

3. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting elec trons and electrode means for forming an electron beam, a first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, at second anode positioned adjacent to said first anode, said second anode having a larger cross-sectional area than said first anode and adapted to intercept that portion of said electron beam not intercepted by said first anode, a beam dispersion electrode positioned within said tube between said electrode means and said anodes, means for connecting an input signal to said beam dispersion electrode, said first anode having a substantially circular crosssectional area substantially equal to the cross-sectional area of said electron beam in the absence of said input signal, said beam dispersion electrode being responsive to said input signal for varying the cross-sectional area of said electron beam as a linear function of the magnitude of said input signal to thereby vary the number of electrons impinging upon each of said anodes, and separate circuit means connected to each of said anodes for deriving conjugate output voltages therefrom Whose magnitude varies respectively in direct and inverse proportion to the square of the magnitude of said input signal.

4. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting electrons and electrode means for forming an electron beam, a first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, a second anode positioned adjacent to said first anode and adapted to intercept that portion of said electron beam not intercepted by said first anode, a beam dispersion electrode positioned within said tube between said electrode means and said anodes, means for connecting an input signal to said beam dispersion electrode, said first anode being in the form of a toroidal disk having an inner diameter substantially equal to the diameter of said electron beam in the absence of said input signal, said beam dispersion electrode being responsive to said input signal for varying the diameter of said electron beam as a linear function of the magnitude of said input signal to thereby vary the number of electrons impinging upon each of said anodes, and separate circuit means connected to each of said anodes for deriving conjugate output voltages therefrom whose magnitudes vary in a non-linear manner.

5. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting electrons, electrode means for forming an electron beam and an accelerating electrode; a source of variable biasing voltage, said accelerating electrode being receptive of said biasing voltage for maintaining substantially constant the number of said beam electrons for a given biasing voltage, a first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, a second anode adjacent to said first anode for intercepting that portion of said electron beam not intercepted by said first anode, said anodes being maintained at the same positive potential relative to said cathode, a beam dispersion electrode positioned within said tube between said accelerating electrode and said anodes and responsive to an input signal and to said biasing voltage for varying the cross-sectional area of said beam and hence the number of electrons striking each of said anodes, first output circuit means connected to said first anode and responsive to the number of electrons impinging thereon for deriving a first output voltage whose magnitude varies substantially as the square of the magnitude of said input signal, and second output circuit means connected to said second anode for deriving a second output voltage which varies inversely with respect to said first output voltage.

6. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting electrons, electrode means for forming an electron beam and an accelerating electrode; a source of variable biasing voltage, said accelerating electrode being receptive of said biasing voltage for maintaining substantially constant the number of said beam electrons for a given biasing voltage, a first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, a second anode adjacent to said first anode for intercepting that portion of said electron beam not intercepted by said first anode, a beam dispersion electrode positioned within said tube between said accelerating electrode and said anodes and responsive to an input signal and said biasing voltage for varying the cross-sectional area of said beam and hence the number of electrons striking each of said anodes, said first anode having a cross-section whose configuration and area are substantially identical to the cross-section of said electron beam in the absence of said input signal, first output circuit means connected to said first anode and responsive to the number of electrons impinging thereon for deriving a first output Voltage whose magnitude varies substantially as the square of the magnitude of said input signal, and second output circuit means connected to said second anode for deriving a second output voltage which varies inversely with respect to said first output voltage.

7. A beam dispersion non-linear output tube comprising an electron gun including a cathode for emitting electrons, electrode means for forming an electron beam and an accelerating electrode; a source of variable biasing voltage, said accelerating electrode being receptive of said biasing voltage for maintaining substantially constant the number of said beam electrons for a given biasing voltage, a first anode axially aligned with said electron beam and adapted to intercept a portion of said electron beam, a second anode adjacent to said first anode for intercepting that portion of said electron beam not intercepted by said first anode, a beam dispersion electrode positioned within said tube between said accelerating electrode and said anodes and responsive to an input signal and to said biasing voltage for varying the cross-sectional area of said beam and hence the number of electrons striking each of said anodes, said first anode being a toroidal disk having an inner diameter substantially equal to the diameter of said electron beam in the absence of said input signal, first output circuit means connected to said first anode and responsive to the number of electrons impinging thereon for deriving a first output voltage whose magnitude varies substantially as the square of the magnitude of said input signal, and second output circuit means connected to said second anode for deriving a second output voltage which varies inversely with respect to said first output voltage.

References Cited in the file of this patent UNITED STATES PATENTS 2,159,818 Plaistowe et a1 May 23, 1939 8 Rust Feb. 20, 1940 Wolfi Feb. 20, 1940 Rust et a1 June 18, 1940 Ziebolz Sept. 26, 1944 Coleman Oct. 30, 1951 

